Method of peripheral nerve reconstruction using a micro suction connector

ABSTRACT

Disclosed is a method of peripheral nerve or blood vessel reconstruction requiring the use of a unique connector. The method employs negative gauge pressure, applied through a port on the connector, to draw the ends of the disrupted nerve or vessel into the connector. Next a biocompatible adhesive is used to cement near the ends of the nerve or vessel circumferentially to the inside of the connector wall, leaving the cut ends touching each other but free of the bio-adhesive. After the placement of the bio-adhesive, additional suction is applied to a port in the temporary housing surrounding the porous connector. This draws the nerve or blood vessel to the full diameter of the connector, maximizing the functionality of a healing blood vessel, providing alignment for disrupted tissue, and improving the circulation of blood around a regenerating nerve.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable

COPYRIGHT STATEMENT

[0002] Not applicable

FEDERAL RESEARCH STATEMENT

[0003] Not Applicable

APPENDIX DATA

[0004] Not Applicable

BACKGROUND OF INVENTION

[0005] Surgical repair of injuries to peripheral nerve tissue may beindicated when damage to the nerve is severe and spontaneousregeneration is unlikely or entirely precluded. The anatomy of theperipheral nervous system can be largely divided into two groups ofcells. The first type of cell is directly involved with the transmissionof the neural impulse signal and is called neurons. A neuron typicallyconsists of a cell body near one end, a synaptic terminal at the other,and an interconnecting axon. A signal is transmitted using an ioniccurrent. This process is referred to as the propagation of an actionpotential.

[0006] The other group of cells in the peripheral nervous system iscollectively called glial cells, which include of a variety of specificcell types that provide support for the neurons. These cells offervarious forms of support. Schwann cells are wrapped around the axon andinsulate the progagation of the action potential. Other cells in thisgroup provide nutrients, physical protection, and immunological defense.The Schwann cells surround the neuron and form an insulating conduit topreserve the signal or action potential traveling in the neuron.Peripheral neurons can regenerate and by using the infrastructure of thedistal severed nerve, they are guided to the appropriate muscle.

[0007] There are three basic levels of injury to nerves. Neuropraxia isthe mildest nerve injury. It is a reversible block in the conduction ofan action potential along a neuron. The neuron remain intact and isfunctional elsewhere, as are the supporting cells. Recovery isspontaneous after removal of the causative agent and does not requiresurgery.

[0008] The intermediate level of nerve injury is called axonotmesis. Theaxon, or the long extension from the neuron cell body, is irreparablydamaged and cannot transmit an action potential.

[0009] The supporting cells surrounding the axon are spared and providea natural guide for the regeneration axon. This type of nerve injuryalso does not require surgical repair.

[0010] The most severe grade of injury damages both the neurons and thesupporting cells and tissue. Without the Schwann cells, as well as thesurrounding connective tissue, the damaged axon is not stimulated toregenerate. It is in this setting that surgical intervention may benefitthe patient.

[0011] The goal of peripheral nerve reconstruction is to rejoin thenerve, facilitating regeneration of the proximal stump by the guidingpresence of the distal part, which has filled with Schwann cells inplace of the degenerated axon. The factors involved in rejoining thenerve segments include mechanically securing the nerve ends in closeproximity to each other while not inhibiting the regeneration process bythe same mechanical means necessary to join the ends. One technique, ifthe nerve is of sufficient size, is suturing the ends together. Anothercurrent technique involves gluing the nerve ends together with abiocompatible adhesive. Guide tubes impregnated with nerve growthfactors have also been used to facilitate the directional growth of theaxon.

[0012] Another potential use for the device and method described hereinis microvasculature reconstruction. Vessels that may be too smallcurrently to reconnect due to time constraints as well as tediousnessmay be candidates for repair using this device and technique.

[0013] The use of the term “microstructure” herein shall include thesmall nerves and the blood vessels that can be joined using this deviceand technique.

SUMMARY OF INVENTION

[0014] While the use of tubes or conduits in the past has been focusedon providing a conduit for the growing proximal neuron, this inventionemploys the connector as a structural device that immobilizes thejoining area of the nerve segments. It also provides a mechanicalbarrier for the microenvironment around the rejoined nerve. Moreimportantly, by using negative gauge pressure during application, itincorporates a means to draw extremely small and flexible fibers intothe connector. Using both the device and the method describe herein, theefficiency and efficacy of microsurgery may be improved.

[0015] Conceptually, the device is a hollow “T” connector, where thearms of the “T” provide the conduit for the microstructure that is beingrepaired. The leg of the “T” is the port where suction is applied todraw in the cut ends of the microstructure. The arm walls of connectorcan be porous but have a temporary housing around them for the purposeof drawing the cut ends into the connector. Once the nerve ends orvessel ends have been drawn into the device, suction can be appliedwithin the surrounding housing to expand the nerve or vessel to the fulldiameter of the connector. Biocompatible adhesive is used to cement thevessels or nerves in place against the inside diameter of the device.

[0016] The device provides protection of the joint as well as a rigidform to allow the microstructure to perform its normal function in thecase of a blood vessel.

BRIEF DESCRIPTION OF DRAWINGS

[0017]FIG. 1. Basic Micro Connector. This illustrates one possiblegeometric configuration of the device as well as a possible woven fibermethod of construction.

[0018]FIG. 2. Porosity of Connector Wall. This depicts a means toprovide suction during adhesion of the microstructure to the inside wallof the device.

[0019]FIG. 3. Housing for Providing Suction through the Connector Wall.The housing would effectively block the pores during the first stage ofdrawing the severed nerves into the

[0020]FIG. 4. One half of a 3-way connector. This shows a variation thatwould allow the device to be placed around an intact nerve serving asthe host for a nerve graft that would be drawn into the remainingconduit.

[0021]FIG. 5. Extended Micro Connector for Graft. The device can be ofany length, accommodating the placement of a graft nerve between twoumbilical ports. This would facilitate repairs to damaged nerves thatwere too short to reconnect directly.

BRIEF DESCRIPTION OF SEQUENCES

[0022] Not Applicable

DETAILED DESCRIPTION

[0023] The device, in its simplest form, consists of an extracellularmatrix (collagen) or other biocompatible material woven or molded intothe shape of a tube with an umbilical port in the middle of the tube.(See FIG. 1.) The device is then saturated with fibrin glue or otherbiocompatible material to make the tube rigid, however leaving the mainconduit porous. (See FIG. 2). Flaring of the ends on the main conduitwould facilitate entry of the microstructures.

[0024] The purpose of the optional porosity of the main conduit is toallow suctioning the microstructure up against the inner wall of theconduit after an adhesive has been applied or injected into space. Ahousing would be placed around the device to effectively block the poresin the main conduit from atmospheric pressure, while the microstructuresare initially suctioned into the device by applying suction at theumbilical port. (See FIG. 3.) After the microstructures are locatedwithin the main conduit and adhesive has been applied, suction can beapplied within the housing. This expands the microstructure up againstthe inside of the device, which would allow for blood flow through ablood vessel, for instance. In the case of nerve repair, drawing theouter sheath of the nerve up against the inner wall of the devicefacilitates blood flow through the vasa nervosum, or the tiny bloodvessels that surround and supply a nerve with blood.

[0025] In addition to acting as a substitute for the normal function ofthe microstructure, the alignment provided by the device, as themicrostructures are adhered to the inner wall, facilitates healing. Inthe case of blood vessels, the device would limit the motion due toexpansion of the vessel from the pulsating blood flow, also facilitatingthe healing process.

[0026] Variations in geometric form include a cross connector to allow athree way splice. The connector could be in two pieces along the planedefined by the two centerlines of the conduits, As shown in FIG. 4. Itcould be snapped together or glued together around the intact vessel ornerve, leaving the third and fourth ports available for the branchedmicrostructure and suction respectively.

[0027] The tube may be impregnated with growth factors such asinsulin-like growth factors, nerve growth factor, or other neurotrophinsto promote axon growth in the case of neural reconstruction. In the useof blood vessel repair, other growth factors such as vascularendothelial growth factor may be considered. The potential exists forcoating the exterior of the tube with a cytostatic material to inhibitfibroblastic activity near the joining sections of nerve or vessel. Thiswould serve to limit the amount of scar tissue formed in this region. Anancillary benefit of using suction to draw the microstructures into themain conduit may be the subsequent concentration of naturally occurringgrowth factors at the joint between the cut ends of the microstructuredue to the suctioning.

[0028] The device could also be coated with heparin or similar substanceto inhibit the formation of thrombi or clots on the device. Gluing themicrostructure up against the inner wall would provide a seal for blood,reducing the dependence on a thrombus to stop bleeding in the case ofrepairing blood vessel.

[0029] A variation in design would include more than one umbilical porton a connector whose length was extended. This would allow for placementof a microstructure graft between the umbilical ports. (See FIG. 5.) Arepair could be made to a shortened microstructure by use of aninterposing graft.

DESCRIPTION OF THE METHOD

[0030] Resection of the proximal stump back to the “functioning” nerve,as determined intraoperatively, prepares the transected peripheral nervebundle. Similarly, trimming a blood vessel back to viable tissue allowsoptimal conditions for healing. Suction is applied to the umbilical portas the cut ends of the microstructure are introduced at both ends of themain conduit. The suctioning approximates the ends of themicrostructures. As suction is continued, with the microstructurestabilized, adhesive is introduced at the entrances of the main conduitwhere the microstructures enter. This provides a permanent stabilizationof the microstructure within the conduit without directly coating thecut ends of the microstructure.

[0031] A variation to suctioning the adhesive into the sleeve would beto remove suction when the ends meet in the middle of the conduit.Fibrin adhesive is injected into the umbilical port, while each end ofthe microstructure is stabilized at the entrances of the main conduit.This alteration would coat the cut ends of the microstructure with theadhesive in addition to the area surrounding the microstructure, shouldthe adhesive include additives to promote growth and healing.

[0032] Following the injection of the adhesive, suction is also appliedto the housing that covers the porous main conduit. See FIG. 3. Thisdraws the microstructure up against the inner wall. In the case of arepair to a blood vessel, prior to introducing the ends into theconnector, the vessels could be ligated or clamped a short distance fromthe repair site, with the blood stripped out. This would prevent loss ofvacuum by blood entering device through the blood vessel.

[0033] Suction could be applied until the adhesive sets. After suctionis removed, the umbilical port can be trimmed off and a dot of adhesiveapplied to the opening to seal the joint. Removal of the clamps orligature will allow inspection for blood leaks.

[0034] Program Listing Deposit

[0035] Not applicable

I claim:
 1. A connecting device which includes a(n): a. main conduit formicrostructures which: i. can be made porous for use with a non-poroushousing, or ii. itself can be made non-porous, and iii. has flared endsfor facilitated entry of the microstructure. b. umbilical port, orports, for the purpose of applying suction.
 2. A surrounding housing orsuitable covering for said porous connecting device to include anumbilical port for the purpose of achieving a negative gauge pressurewithin said housing
 3. A method of utilization for said device toinclude: a. Suctioning or negative gauge pressure within themicro-connector to draw microstructures into said device b. Suctioningor negative gauge pressure within the surrounding housing to drawmicrostructures up against the inner wall of the said connecting devicec. The use of a bio-adhesive to attach the microstructure to the insideof the connector.